BANGKOK (Reuters) - Asian countries should intensify their war on a deadly bird flu that shows no signs of receding with fresh outbreaks in China and which threatens to evolve into a SARS-like epidemic, health experts said on Thursday.

The World Health Organization said authorities were rushing to declare the disease ravaging their poultry flocks under control and it warned people were still at risk from the H5N1 virus that has killed 22 people in Asia. "We are in an emergency, urgency mode," Bjorn Melgaard, the WHO representative in Thailand, told regional health experts gathered in Bangkok to compare notes on fighting the virus.

"The bird epidemic is unfolding and continuing to spread at an unprecedented rate."

China confirmed three outbreaks among poultry in three provinces on Thursday, but so far no human cases of the virus that has killed 15 Vietnamese and seven Thais.

In Vietnam, a 16-month-old baby girl was confirmed with H5N1 on Thursday, a day after a three-year-old boy died in the country's latest death from the disease.

Melgaard recalled that a year ago Asia faced an even deadlier epidemic of Severe Acute Respiratory Syndrome (SARS) that killed more than 800 people before it was finally brought under control.

"We are again confronting yet another emerging disease with the potential of causing a global epidemic," he said, urging nations not to relax their surveillance and detection efforts.

"We would expect that we will see human cases in other countries that have the bird epidemic," Melgaard said.

Thailand and Vietnam, where all the human cases have been reported, have talked about declaring victory over the virulent H5N1 virus in a matter of weeks.

Thailand, which found recurrences of the disease in 14 areas this month, still says it expects to do so next month.

The Thai government, with an eye on the country's shattered $1 billion-a year poultry trade, is eager to resume exports and sent a high-level delegation to top-buyer Japan this week.

VIGILANCE

In Vietnam, Premier Phan Van Khai urged officials not to let their guard down despite his earlier orders that the disease be brought under control this month.

Khai said they "must continue directing prevention efforts without allowing any early complacency among certain agencies, officials and residents," said the state-run Vietnam news daily.

Outbreaks have been reported in 57 of Vietnam's 64 provinces and 27 million birds have either died or been destroyed.

Another 30 million birds have been slaughtered in Thailand, and Taiwan said on Thursday it would slaughter 13,000 fowl as a milder form of bird flu hit two more chicken farms.

The U.N.'s Food and Agriculture Organization said it would be at least a year, perhaps never, before the virus was under control. And health experts say the risk of a human pandemic grows the longer the virus lingers.

"If you allow this virus to keep on entering the human population over and over again, you could have the virus learning to transmit effectively from human to human," said Malik Peiris, an influenza expert at the University of Hong Kong.

"This is clearly what happened with SARS last year."

"INEVITABLE" PIGS WILL BE INFECTED

Experts worry the virus could infect a person who also has the human flu virus, allowing it to mutate into a strain that could spread through people with no immunity.

This month there were fears, quashed quickly by the FAO, that the virus had infected pigs in Vietnam and that could speed up the mutation process.

But Peiris said it may be inevitable. Hong Kong studies on pigs imported from China had found them infected with the human influenza virus.

With pigs and chickens living side-by-side on most farms in southern China, where outbreaks of avian influenza among poultry and ducks have been reported, the threat of human and H5N1 viruses mixing in pigs to create a "super virus" is real.

"Inevitably, pigs are going to be exposed to this (H5N1) virus," Peiris told the Bangkok meeting.

Pet cats and a rare clouded leopard have already died of bird flu after eating infected chicken in Thailand, increasing fears the disease can jump easily to other non-avian species.

Thai authorities were also checking nearly 200 cows and buffaloes that apparently died of cold weather to be sure they were not infected with the virus.